Flyback converters are well suited for applications requiring a wide input voltage range, or a high voltage output with galvanic isolation between the input and output of the converter. The operation of a flyback converter begins by grounding a primary side of a transformer with a switch. Consequently, current flows in the primary, thus inducing a magnetic flux in the core of the transformer, which tends to oppose the primary current. By choosing a transformer with reverse polarity windings, (e.g. the secondary windings are wound on the core in the opposing rotational direction to the primary windings), the secondary current will not flow when the primary current flows, due to the blocking action of a rectifying diode on the secondary side. When the primary current is terminated, the magnetic flux in the core will induce a secondary current in an opposing direction to the flux, which will transfer the stored energy from the core to the secondary side with appropriate voltage amplification depending upon the transformer's turns ratio.
Conventionally, the amplitude of the primary current is used to estimate the amplitude of the secondary current, and thus enable current regulation of the converter. The flyback converter has a resonant topology wherein an oscillating resonant waveform will be presented to the switch on the primary side due to a leakage inductance of the transformer and a capacitance of the switch. The resonant waveform causes a negative current to flow through the switch, thus introducing an error in conventional methods of current regulation. There may also be high frequency oscillations or ringing across the switch due to the rapid activation of the switch interacting with the leakage inductance. Furthermore, it is desirable to regulate the converter based on power consumption as well as current to facilitate the design and operation of the converter, while maintaining galvanic isolation between the primary and secondary sides.